Commit graph

3 commits

Author SHA1 Message Date
sterni
5174c21637 fix(nix/tag): correct no match check in discr
It uses discrDef internally, but passes `null` as the default tag name,
causing Nix to drop the attribute and return an empty attribute set if
the default case is hit. Consequently we need to check for the empty
attribute set, not `null` to figure out if there was no match found.

We can also test this behavior using `assertThrows` which was introduced
after the tag library was originally written.

Change-Id: I45adb2f9602762dfc867956323fb3f5ae4c8bd1d
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6904
Autosubmit: sterni <sternenseemann@systemli.org>
Reviewed-by: Profpatsch <mail@profpatsch.de>
Tested-by: BuildkiteCI
2022-10-09 13:25:14 +00:00
Vincent Ambo
aa122cbae7 style: format entire depot with nixpkgs-fmt
This CL can be used to compare the style of nixpkgs-fmt against other
formatters (nixpkgs, alejandra).

Change-Id: I87c6abff6bcb546b02ead15ad0405f81e01b6d9e
Reviewed-on: https://cl.tvl.fyi/c/depot/+/4397
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
Reviewed-by: lukegb <lukegb@tvl.fyi>
Reviewed-by: wpcarro <wpcarro@gmail.com>
Reviewed-by: Profpatsch <mail@profpatsch.de>
Reviewed-by: kanepyork <rikingcoding@gmail.com>
Reviewed-by: tazjin <tazjin@tvl.su>
Reviewed-by: cynthia <cynthia@tvl.fyi>
Reviewed-by: edef <edef@edef.eu>
Reviewed-by: eta <tvl@eta.st>
Reviewed-by: grfn <grfn@gws.fyi>
2022-01-31 16:11:53 +00:00
Profpatsch
e4a7704583 feat(nix): add nix.tag, a way of discriminating via tagged unions
Introduces the concept of a “tag”, a single-keyed attrset which
annotates a nix value with a name.
This can be used to implement tagged unions (by implying the list of
possible tags is well-known), which has some overlap with how
`nix.yants` does it.

However, the more fascinating use-case is in concert with a
so-called discriminator, `match` and hylomorphisms.

The discriminator can take a nix value, and add tags to it based on
some predicate.
With `match`, we can then use that information to convert the
discriminated values again.
With `hylo`, we can combine both the “constructive” discriminator step
with the “destructive” match step to recursively walk over a nix data
structure (based on a description of how to recurse, e.g. through attrset
values or list values), and then apply a transformation in one go.

Change-Id: Ia335ca8b0881447fbbcb6bcd80f49feb835f1715
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2434
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
2021-01-30 15:41:08 +00:00